It is common practice to inspect rolled strips to evaluate the state of wear of the rolling cylinders in the technical rolling field. The possible need to change the rolling cylinders is determined according to the quality of the strip, i.e. according to the number, extent and degree of acceptability of the faults detected thereon.
In order to evaluate the quality of a rolled strip wound in a oil it is also required to evaluate the surface quality of the inner coil face, i.e. the concave face facing the winding axis of the coil, even at the innermost turns. This is only possible by unwinding the coil.
To this end, inspection stations which form an off-line apparatus can be used, even to perform mechanical measurements, such as for example thickness or hardness measurements, on strip samples. The main problem which influences the design and construction of such inspection stations is represented by the very thick wound strips or those with high yield strength tending to maintain the curved shape (the so-called “coil set”) also after the unwinding. Straightening the strip, e.g. by means of further mechanical members, such as rolls or tables, is thus required in order to facilitate the inspection operations. However, to preserve the strip quality without modifying the mechanical surface features of the zone to be inspected, the contact between the strip and the mechanical members (rolls, tables, etc.) used to straighten it should be limited as much as possible.
For this reason, it is known to provide at least two different types of inspection stations, which can be used exclusively for strips of small maximum thicknesses, e.g. up to a maximum thickness of about 2 mm, or for thicker strips, e.g. thicker than 2 mm, respectively.